Which of the following symptoms could indicate a serious adverse effect in a patient receiving clozapine?

Fever and sore throat are particularly significant symptoms in a patient receiving clozapine because they may indicate agranulocytosis, a potentially serious and life-threatening side effect associated with this medication. Clozapine can significantly lower white blood cell counts, increasing the risk of infections. Fever could suggest the presence of an infection, while a sore throat can signal a reduced immune response that often accompanies agranulocytosis. Due to these risks, patients on clozapine require regular monitoring of their white blood cell counts to detect any hematologic issues early.

Increased energy levels might indicate an improvement in mood or psychotic symptoms often seen in patients treated with clozapine, while seasonal allergies generally do not relate directly to the side effects of antipsychotics like clozapine. Joint pain could stem from various causes but is not specifically tied to the serious adverse effects seen with clozapine therapy.